1. Field of the Invention
The present invention relates to an infrared-light-absorption gas concentration measurement device.
2. Description of the Related Art
Various types of gas concentration measurement devices for analyzing various types of exhaust, gas contained in the atmosphere, or gas contained in the air in a building have been developed. In particular, infrared-light-absorption gas concentration measurement devices are used to analyze sample gas because the sample gas absorbs infrared light in a specific wavelength range.
International Publication No. 01/27596, for example, discloses an infrared-light-absorption gas concentration measurement device. In the gas concentration measurement device disclosed in International Publication No. 01/27596, an anti-reflection film is applied to inner walls of an analysis chamber (sample cell) that defines a flow channel for the sample gas. Accordingly, the risk of the infrared light being incident on a band pass filter, which is provided on a surface of a detector, at an angle greater than a predetermined angle is somewhat reduced.
The anti-reflection film disclosed in International Publication No. 01/27596 must be made of a material including a reflectance close to zero. Thus, the material of the anti-reflection film is limited. If an inexpensive material including a reflectance that is not close to zero is used, the infrared light is reflected by the anti-reflection film such that the reflected infrared light is incident on the band pass filter at an angle greater than the predetermined angle. Thus, the transmission band of the band pass filter is shifted and the measurement accuracy of the gas concentration measurement device decreases.
Therefore, a gas concentration measurement device including a new structure that is able to be substituted for the anti-reflection film made of a specified material and that can reduce the risk of the reflected infrared light being incident on the band pass filter at an angle greater than the predetermined angle is needed.